The Windows CE operating system was designed by Microsoft Corporation for limited-resource computers such as palmtop and other portable computers. Because of the limited amount of memory in such computers, Windows CE supports raster fonts rather than the more flexible TrueType fonts that are supported by Microsoft's desktop operating systems such as the Windows 95 and Windows NT operating systems.
TrueType is an outline font technology introduced in 1991 as a means of including high-grade fonts within the Apple Macintosh and Microsoft Windows operating systems. TrueType is a WYSIWYG font technology, which means that the printed output of TrueType fonts is identical to what appears on the screen.
TrueType consists of two parts: the so-called "engine" built into the operating system that does the work of generating and displaying the fonts, and the fonts themselves, which are stored in separate files on disk and called into use as needed. Because the fonts are stored separately, a user can add additional TrueType fonts to his or her system simply by adding additional font files. TrueType is also built into some peripheral devices--primarily printers--to help printers generate and print the individual characters, thus speeding up the printing process.
TrueType fonts are outline fonts; that is, the shapes of the characters are defined in terms of mathematically generated lines and curves rather than by patterns of dots. The advantage of outline fonts is that characters can be efficiently scaled to any size.
Raster fonts, in contrast, represent characters as bitmaps--patterns of pixels or dots. One significant disadvantage of raster fonts is they cannot be effectively scaled to different sizes--a single font is normally used only for a single character size. An advantage, however, is that a raster font of a particular character size is usually smaller than a corresponding TrueType font. Furthermore, the support software required to render and display raster fonts requires less memory and executes more quickly than the corresponding support software for rendering and displaying TrueType outline fonts.
The decision not to support TrueType fonts in the Windows CE environment was not without drawbacks, however. Connectivity is a key feature of Windows CE and of the computers that run Windows CE. Typically, a Windows CE computer is used in conjunction with a primary desktop computer. Documents and other files are downloaded to the palmtop computer, and the palmtop computer is used to access, maintain, and modify the documents and files when the desktop computer is not available. Extensive synchronization capabilities have been built into the Windows CE operating system as a further convenience for those who use their portable computers in conjunction with a more conventional desktop computer.
A great number of files that are created on a Windows 95 or Windows NT computer make use of TrueType fonts--fonts that are unavailable on a portable computer running Windows CE. When documents utilizing TrueType fonts are downloaded to a Windows CE device and loaded into a resident program such as a word processor, the TrueType font information is retained in the document so that it can be restored when the document is returned to the desktop computer. While the document is displayed and used on the Windows CE device, however, any non-supported font such as a TrueType font is mapped for display purposes to the closest matching raster font available on the Windows CE computer.
The disadvantage to this scheme is that characters often do not appear as they were intended to appear when they are viewed on the Windows CE portable computer. The invention remedies this problem.